Interspinous vertebral and lumbosacral stabilization devices and methods of use

ABSTRACT

Implantable devices are provided for stabilizing adjacent vertebrae and the lumbosacral region of a patient. The devices can comprise an interspinous flexible spacer body having a substantially U-shape comprising a superior section, inferior section, and a midsection extending therebetween. The superior and/or inferior sections can include a pair of lateral walls configured to engage a spinous process of a vertebra. Fixation caps can be provided for securing a spinous process of a vertebra to the flexible spacer body. To secure the flexible spacer body between the lumbar vertebra and an adjacent vertebra, an anchor assembly is provided. Also provided are methods of using the implantable devices to stabilize a patient&#39;s spine.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. patent application Ser.No. 11/400,586, entitled “INTERSPINOUS VERTEBRAL AND LUMBOSACRALSTABILIZATION DEVICES AND METHODS OF USE,” filed Apr. 7, 2006, now U.S.Pat. No. 8,470,000, which claims priority to U.S. ProvisionalApplication No. 60/669,346, filed on Apr. 8, 2005, both of which areincorporated by reference in their entirety.

FIELD

The present invention relates to devices and methods for treating spinalconditions, and specifically to vertebral stabilization devices andmethods of using such devices for stabilizing adjacent vertebrae. Morespecifically, the present invention relates to interspinous vertebralstabilization devices for placement between the spinous processes of twoor more vertebrae and, even more specifically, to lumbosacralstabilization devices for placement between a lumbar vertebra and anadjacent vertebra and methods of using such devices.

BACKGROUND

Diseases of the spine cause significant morbidity. These diseasesinclude abnormalities of the vertebrae, the intervertebral discs, thefacet joints, and connective tissue around the spine. Theseabnormalities can be due to a number of causes, including mechanicalinjury or degenerative disc disease. Such abnormalities can causeinstability to the spine, allowing the vertebral column to becomemisaligned and producing micromotion between adjacent vertebrae.Vertebral misalignment and micromotion may result in wear to thevertebral bony surfaces and ultimately cause severe pain. Further, theseconditions are often chronic and progressive problems.

The treatments for spinal disorders may include long-term medicalmanagement or surgery. Medical management is generally directed atcontrolling the symptoms, such as pain, rather than correcting theunderlying problem. For some patients this may require chronic use ofpain medications, which may alter patient mental state or cause othernegative side effects.

Another treatment option is surgery, which is often highly invasive andmay significantly alter the spinal anatomy and function. For example,one surgical treatment for certain spinal conditions includes spinalfusion, whereby two or more vertebrae may be joined using bone graftsand/or synthetic implants. The fusion process is irreversible and maysignificantly alter vertebral range-of-motion. Further, current surgicalprocedures are often only applicable to patients in a significantlyprogressed disease state.

Consequently, spinal surgeons have begun to develop more advancedsurgical procedures and spinal stabilization and/or repair devices thatare less invasive, may be reversible, and cause a less drasticalteration in the patient's normal anatomy and spinal function. Theseprocedures may be used in an earlier stage of disease progression and,in some situations, may even stop or reverse disease progression.

Recently, a variety of interspinous stabilization devices have becomeavailable. These devices may be implanted between the spinous processesof two or more adjacent vertebrae. By stabilizing the spinous processesin this way, significant stress may be taken off the intervertebraldiscs to prevent disease progression or to improve conditions such asspinal stenosis. In addition, vertebral motion may be controlled withoutseverely altering spinal anatomy.

Current interspinous vertebral implants are configured to be attached tothe spinous processes of two or more adjacent vertebrae. Because thesacrum has a very small or non-existent spinous process, these devicescannot be implanted between the fifth lumbar vertebra (L5) and the firstsacral vertebra (S1). However, many patients have spinal conditions thataffect the L5 and sacral vertebrae. It would therefore be desirable toprovide an interspinous vertebral stabilization device which can beimplanted between the sacrum and a lumbar vertebra.

SUMMARY OF THE INVENTION

The present invention includes interspinous vertebral and lumbosacralstabilization devices, and methods of using these devices for treatingspinal instability conditions. The invention includes interspinousvertebral stabilization devices adapted for placement between thespinous processes of two or more adjacent vertebrae. The invention alsoincludes lumbar stabilization devices adapted to be placed between alumbar vertebra and an adjacent vertebra, including the first sacralvertebra (S1), to stabilize the lumbosacral region of a patient, andmethod for using such devices.

One aspect of the invention includes a device for stabilizing a vertebraadjacent or near a sacrum. The device may comprise an implantable,flexible U-shaped spacer body comprising an inferior section, a superiorsection, a midsection, and a pair of lateral walls extending from thesuperior section for engaging a spinous process of a lumbar vertebra.The device may also include an anchor assembly for securing the spacerbody between a lumbar vertebra and an adjacent vertebra, including thesacrum.

A second aspect of the invention includes an interspinous stabilizationdevice comprising a support rod and a flexible U-shaped spacer body. Thespacer body comprises an inferior section, a superior section, and amidsection therebetween. A pair of lateral walls extends from thesuperior section for engaging a spinous process of a lumbar vertebra.The inferior section may include a base portion configured to couplewith the support rod. The device may further comprise at least onefixation element for securing the support rod to an adjacent vertebra.

A third aspect of the invention includes a lumbosacral interspinousstabilization device comprising a flexible, U-shaped spacer body forimplantation between a lumbar vertebra and the sacrum. The spacer bodycomprises an inferior section, a superior section, and a midsectiontherebetween. A pair of lateral walls extends from the superior sectionfor engaging a spinous process of a lumbar vertebra. The inferiorsection may include at least one projection that forms a grippingportion for engagement with the sacrum.

A fourth aspect of the invention includes an implantable device forstabilizing an interspinous region of a patient comprising a flexibleU-shaped spacer body having an inferior section, a superior section, anda midsection extending therebetween. The device may also provide afixation cap for engaging the superior section of the spacer body. Thecap is configured to secure a spinous process of a vertebra to thespacer body. Also provided is an anchor assembly for securing the spacerbody between the vertebra and an adjacent vertebra.

A fifth aspect of the invention includes an interspinous vertebralstabilization device comprising a flexible U-shaped spacer body. Thespacer body comprises an inferior section, a superior section, and amidsection therebetween. The spacer body may be configured for placementwithin the interspinous space of two adjacent vertebrae. The device mayalso provide a pair of fixation caps, each cap being configured toengage the superior or inferior section of the spacer body. Whenattached to the spacer body, the caps secure the spinous processes ofthe two adjacent vertebrae to the spacer body.

A sixth aspect of the invention includes an interspinous vertebralstabilization device comprising a flexible U-shaped spacer body. Thespacer body comprises an inferior section including a pair of lateralwalls extending therefrom for engaging a spinous process of a vertebra.The spacer body further comprises a superior section including a pair oflateral walls extending therefrom for engaging a spinous process of anadjacent vertebra. A midsection extends between the inferior andsuperior sections. The spacer body may be configured for placementwithin the interspinous space of two adjacent vertebrae. The device mayalso include a pair of fixation caps, each cap being configured forengagement with of the two pairs of lateral walls. When attached to thespacer body, the caps secure the spinous processes of the two adjacentvertebrae to the spacer body.

A seventh aspect of the invention includes an interspinous vertebralstabilization device comprising a flexible U-shaped spacer body. Thespacer body comprises an inferior section including a pair of lateralwalls extending therefrom for engaging a spinous process of a vertebra.The spacer body further comprises a superior section including a pair oflateral walls extending therefrom for engaging a spinous process of anadjacent vertebra. A midsection extends between the inferior andsuperior sections. At least one of the lateral walls is selectivelymovable with respect to another of the lateral walls. The movablelateral wall can be selectively positioned to secure the spinous processof one of the two adjacent vertebrae to the spacer body.

Also provided are methods for stabilizing the lumbosacral region of apatient using the devices of the present invention. Methods forstabilizing the interspinous region of adjacent vertebrae using thedevices of the present invention are also provided.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

Additional objects and advantages of the invention will be set forth inpart in the description which follows or may be learned by practice ofthe invention. The objects and advantages of the invention will berealized and attained by means of the elements and combinationsparticularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary embodiment of an interspinouslumbosacral stabilization device according to this invention;

FIGS. 2A-2B provide side views of a spacer body under resting andcompressed states, respectively, according to exemplary disclosedembodiments;

FIGS. 3A-3C provide side views of a spacer body having varying thicknessalong its length, according to exemplary disclosed embodiments;

FIG. 4A provides a perspective view of a spacer body having a variablewidth along its length, according to another exemplary disclosedembodiment;

FIG. 4B provides a rear view of the spacer body of FIG. 4A;

FIG. 5 provides a side view of a spacer body, according to an exemplarydisclosed embodiment;

FIGS. 6A-6C provide rear views of a spacer body, according to exemplarydisclosed embodiments;

FIG. 7A provides a rear view of a spacer body including barbs, accordingto an exemplary disclosed embodiment;

FIG. 7B provides a side view of a spacer body including barbs, accordingto an exemplary disclosed embodiment;

FIG. 8A provides a partial top-down perspective view of a spacer bodyincluding curved lateral walls, according to an exemplary disclosedembodiment;

FIG. 8B provides an enlarged view showing details of FIG. 8A;

FIG. 9A provides a partial perspective view of a spacer body includingcurved lateral walls, according to an exemplary disclosed embodiment;

FIG. 9B provides a partial perspective view of the spacer body of FIG.9A implanted within a patient;

FIG. 10A provides a partial perspective view of a spacer body having adetachable lateral wall, according to an exemplary disclosed embodiment;

FIGS. 10B and 10C provide partial perspective views of the spacer bodyof FIG. 10A implanted within a patient;

FIG. 11A provides a partial perspective view of a spacer body having adetachable lateral wall, according to an exemplary disclosed embodiment;

FIGS. 11B and 11C provide partial perspective views of the spacer bodyof FIG. 11A implanted within a patient;

FIG. 12A provides a partial perspective view of a spacer body having adetachable lateral wall, according to an exemplary disclosed embodiment;

FIGS. 12B and 12C provide partial perspective views of the spacer bodyof FIG. 12A implanted within a patient;

FIG. 13A provides a partial perspective view of a spacer body having ahinged lateral wall, according to an exemplary disclosed embodiment;

FIGS. 13B and 13C provide partial perspective views of the spacer bodyof FIG. 13A implanted within a patient;

FIG. 14A provides a partial exploded view of a spacer body having afoldable lateral wall, according to an exemplary disclosed embodiment;

FIGS. 14B and 14C provide partial perspective views of the spacer bodyof FIG. 14A implanted within a patient;

FIG. 14D provides an enlarged view showing details of FIG. 14C;

FIG. 15 provides a side view of a bone fastener, according to anexemplary disclosed embodiment;

FIG. 16A provides a cross-sectional view of the bone fastener of FIG.16C, according to an exemplary disclosed embodiment;

FIG. 16B provides an enlarged view showing details of FIG. 16A;

FIG. 16C provides a side view of the bone fastener of FIG. 16A;

FIG. 16D provides an enlarged view showing details of FIG. 16C.

FIG. 17A provides a perspective view of a spacer body and flexiblefixation member, according to an exemplary disclosed embodiment;

FIG. 17B illustrates the device of FIG. 17A positioned between an L5spinous process and a sacrum, according to an exemplary disclosedembodiment;

FIG. 18A provides a partial perspective view of a spacer body having arigid fixation member, according to an exemplary disclosed embodiment;

FIG. 18B provides an enlarged view showing details of FIG. 18A;

FIG. 18C provides a partial perspective view of the spacer body of FIG.18A implanted within a patient;

FIG. 19A provides a partial perspective view of a spacer body having arigid fixation member, according to an exemplary disclosed embodiment;

FIG. 19B provides an enlarged view showing details of FIG. 19A;

FIG. 19C provides a partial perspective view of the spacer body of FIG.19A implanted within a patient;

FIG. 20A provides a partial perspective view of a spacer body having arigid fixation member, according to an exemplary disclosed embodiment;

FIG. 20B provides an enlarged view showing details of FIG. 20A;

FIG. 20C provides a partial perspective view of the spacer body of FIG.20A implanted within a patient;

FIG. 21 provides a side view of a spacer body, according to anotherexemplary disclosed embodiment;

FIG. 22A provides a side perspective view of a spacer body, according toyet another exemplary disclosed embodiment;

FIG. 22B provides a perspective view of the spacer body of FIG. 22Aimplanted within a patient;

FIG. 23 provides a side view of a spacer body, according to a furtherexemplary disclosed embodiment;

FIG. 24 provides a rear view of a spacer body and fixation rod,according to an exemplary disclosed embodiment;

FIGS. 25A-25C provide cross-sectional views of fixation rods, accordingto exemplary disclosed embodiments;

FIG. 26A provides a front view of a fixation rod, according to anotherexemplary disclosed embodiment;

FIG. 26B provides an exploded perspective view of a spacer body and thefixation rod of FIG. 26A, according to an exemplary disclosedembodiment;

FIGS. 27A-27C illustrate front views of alternate fixation rods,according to exemplary disclosed embodiments;

FIG. 28A provides a perspective view of a spacer body, according to anexemplary disclosed embodiment;

FIG. 28B provides a perspective view of a device including the spacerbody of FIG. 28A, implanted in a patient;

FIG. 29A provides an exploded view of a spacer body and rod, accordingto an exemplary disclosed embodiment;

FIG. 29B provides a perspective view of a device including the spacerbody and rod of FIG. 29A;

FIG. 29C provides a partial cross-sectional view of the device of FIG.29B implanted in a patient;

FIG. 30 provides an exploded perspective view of a polyaxial screwsystem, according to an exemplary disclosed embodiment;

FIG. 31A provides a cross-sectional view of the polyaxial screw systemof FIG. 30 along lines A-A;

FIG. 31B provides a cross-sectional view of the polyaxial screw systemof FIG. 30 along lines B-B;

FIG. 31C provides an enlarged view showing details of FIG. 31A;

FIG. 31D provides an enlarged view showing details of FIG. 31B;

FIG. 32A provides a side perspective view of a spacer body, according toan exemplary disclosed embodiment;

FIG. 32B provides a partial side perspective view of the spacer body ofFIG. 32A implanted in a patient;

FIG. 33A provides a side perspective view of a spacer body, according toan exemplary disclosed embodiment;

FIG. 33B provides a partial side perspective view of the spacer body ofFIG. 33A implanted in a patient;

FIG. 34A provides a side perspective view of a spacer body, according toan exemplary disclosed embodiment;

FIG. 34B provides a partial side perspective view of the spacer body ofFIG. 34A implanted in a patient;

FIG. 35A provides a side perspective view of a spacer body, according toan exemplary disclosed embodiment;

FIG. 35B provides a partial side perspective view of the spacer body ofFIG. 35A implanted in a patient;

FIG. 36A provides a side perspective view of a spacer body, according toan exemplary disclosed embodiment;

FIG. 36B provides a partial side perspective view of the spacer body ofFIG. 36A implanted in a patient;

FIG. 37A provides a side perspective view of a spacer body, according toyet another exemplary disclosed embodiment;

FIG. 37B provides a partial side perspective view of the spacer body ofFIG. 37A implanted in a patient;

FIG. 38A provides an exploded perspective view of a spacer body,according to another exemplary disclosed embodiment;

FIG. 38B provides a side perspective view of the spacer body of FIG. 38Aassembled;

FIG. 39 provides a perspective view of the spacer body of FIGS. 38A and38B implanted in a patient;

FIG. 40A provides an exploded perspective view of a spacer body,according to yet another exemplary disclosed embodiment;

FIG. 40B provides a side perspective view of the spacer body of FIG. 40Aassembled; and

FIG. 41 provides a perspective view of the spacer body of FIGS. 40A and40B implanted in a patient.

DESCRIPTION OF THE EMBODIMENTS

The present disclosure provides implantable devices for stabilizingvertebrae when placed between the spinous processes of adjacentvertebrae, and for stabilizing the lumbosacral region of a patient byplacement of the device between a lumbar vertebra and an adjacentvertebra, including the first sacral vertebra (S1). As shown in anexemplary embodiment depicted in FIG. 1, the implant or device 10comprises a spacer body 12 that is configured to be implanted betweenthe spinous process of a lumbar vertebra, such as the fifth lumbar (L5)spinous process, and an adjacent vertebra. An anchor assembly 14 isprovided to secure the spacer body 12 to the adjacent vertebra, whichcan be, for example, the first sacral vertebra (S1).

The anchor assembly 14 may include a support or a fixation rod 16 tohelp maintain the spacer body 12 in a proper position with respect tothe spine. One or more fixation elements, such as, for example, boneanchors 18 may be used to firmly attach the support or fixation rod 16onto the patient's sacrum. As illustrated in FIG. 1, the spacer body 12may be connected to the fixation rod 16 at a base portion 62.Collectively, the spacer body 12, support rod 16, and bone anchors 18form an interspinous stabilization assembly for stabilizing a lumbarvertebra such as the fifth lumbar vertebra (L5) adjacent the sacrum.

The spacer body 12 may have various shapes, thicknesses, and materials.In one embodiment, the spacer body 12 may include a midsection 30extending between an inferior section 32 and a superior section 34, asshown in FIG. 1. When implanted in a patient, the superior section 34 isconfigured to contact a portion of a spinous process, while the inferiorsection 32 is configured to connect with fixation rod 16. In oneembodiment, the midsection 30, inferior section 32, and superior section34 may together form a substantially U-shaped spacer body 12.

The spacer body 12 may be configured to be flexible and/or bendable,such as, for example, by providing an extendable and/or compressiblemidsection 30. During spinal extension, a spinous process may exert aninferiorly-directed force on the superior section 34. Likewise, duringspinal extension, the fixation rod 16 and/or sacrum may exert asuperiorly-directed force on the inferior section 32. As shown in FIGS.2A and 2B, these forces may cause the superior section 34 and theinferior section 32 to be brought closer together (FIG. 2B) from aresting state in which no external force acts upon the spacer body 12(FIG. 2A). Compressibility in this way may allow the spacer body 12 toreversibly deform to allow some degree of spinal extension. Thus, themidsection 30 acts as a flexible hinge, allowing the superior section 34and inferior section 32 to move away from or towards one another.

In addition, the thickness and physical properties of the superiorsection 34 and/or the inferior section 32 may be selected to allow thesuperior section 34 and/or the inferior section 32 to bend under ampleload. Flexibility (i.e., extendability and/or compressibility) may allowthe spacer body 12 to better respond to some normal patient movements.For example, a spacer body 12 having limited compressibility may allow acertain degree of spinal extension, while also controlling spinalflexion, rotation, and/or lateral bending.

The flexibility and/or compressibility of spacer body 12 may be selectedbased on the body habitus of the patient in whom the device 10 is to beimplanted, based on the desired range of motion, and based on variousclinical factors. Such clinical factors may include co-morbidconditions, extent of disease, prior surgery, etc. For some patients, avery rigid spacer body 12 may be desirable. For other patients, a moreflexible and compressible spacer body 12 may be selected by the surgeon.

The flexibility and/or compressibility of the spacer body 12 may becontrolled in a number of ways. For example, the spacer body 12 may beformed from a variety of different materials. In one embodiment, thespacer body 12 may be formed from a single material. Alternatively, thespacer body 12 may include a combination of materials such that thematerials forming the midsection 30, inferior section 32, and superiorsection 34 can differ to provide each of the sections with varyingdegrees of flexibility and/or compressibility. The specific materialsincluded in each section of the spacer body 12 may be selected based ona desired degree of flexibility and/or compressibility or to providebiocompatibility and/or bioactive characteristics.

A number of biocompatible materials are suitable for forming the spacerbody 12 of the present disclosure. For example, in one embodiment, thespacer body 12 may be formed from a medical grade metal such as titaniumor titanium alloy. The spacer body 12 may also be formed from, e.g.,stainless steel, cobalt chrome, ceramics, and/or polymeric materials,such as ultra-high molecular-weight polyethylene (UHMWPE) andpolyetheretherketone (PEEK), either alone or in combination with anotherone of the suitable materials.

Another way to provide flexibility and/or compressibility to the spacerbody 12 is to vary the dimensions of the spacer body 12, such that thedegree of flexibility relates to the relative dimensions of the spacerbody 12. For example, the spacer body 12 may have a variety of differentthicknesses along its length. The thicknesses may be selected to producea desired degree of flexibility and compressibility. Further, the spacerbody 12 may have a variable thickness in one or more different sections.FIGS. 3A-3C illustrate a variety of thickness configurations for thespacer body 12, in which the midsection 30 has a thickness t.sub.1, theinferior section 32 has a thickness t.sub.2 and the superior section 34has a thickness t.sub.3. In one embodiment, thickness t.sub.1, thicknesst.sub.2, and thickness t.sub.3 may be approximately equal (FIG. 3A). Inanother embodiment, thickness t.sub.1 may be greater than thicknessest.sub.2 and t.sub.3 (FIG. 3B), and in still another embodiment,thickness t.sub.1 may be less than thicknesses t.sub.2 and t.sub.3 (FIG.3C). Hence, as shown in FIGS. 3B and 3C, the thickness and consequentlythe flexibility of the spacer body 12 can vary along its length.

Yet another way to affect the flexibility of the spacer body 12 is tovary the width of the body 12 along its length. For instance, asillustrated in FIG. 4A, the spacer body 12 can have a width at themidsection 30 that is less than the width of either the inferior section32 or superior section 34. Such a configuration would provide the spacerbody 12 with an hourglass-like configuration, when viewed from the rearas shown in FIG. 4B.

To limit the compression of the midsection 30 of the spacer body 12, itis contemplated that a bearing cushion (not shown) can be placed betweenthe superior 34 and inferior sections 32 within the spacer body 12. Thebearing cushion can be similar to the one described in U.S. Pat. No.5,645,599 to Samani, the contents of which are hereby incorporated inits entirety by reference. The bearing cushion makes it possible tolimit the closing together of the two sections 32, 34 and to ensure asupplementary cushioning of the vertebra 4 if such is desired. Thecushion can be made of a suitable elastic material, either wovenmaterial or synthetic material, and can be fixed to the sections 32, 34by any suitable means, such as for example by adhesive bonding.

To engage the spinous process of a vertebra, the spacer body 12 may beprovided with a pair of lateral walls or brackets 36 that extend fromthe superior section 34, as shown in FIG. 5. The pair of lateral walls36 define a stirrup 38 for receiving a spinous process. In oneembodiment, the lateral walls or brackets 36 may be configured to engagethe spinous process of a lumbar vertebra near the sacrum and secure thespacer body 12 to the spinous process. For example, the brackets 36 maybe configured to engage the spinous process of the fifth lumbar vertebra(L5) adjacent the sacrum.

The lateral walls 36 may have a number of orientations with respect tothe spacer body 12. For example, as shown in FIGS. 6A-6C, lateral walls36 may extend in a variety of angles with respect to the superiorsection 34. In one embodiment, the lateral walls 36 may form a 90 degreeangle with respect to the superior section 34 (FIG. 6A). In otherembodiments, the lateral walls 36 may form an obtuse angle (FIG. 6B) oran acute angle (FIG. 6C) with respect to the superior section 34. Inaddition, spacer bodies 12 can be provided with lateral walls 36 ofvarious sizes or heights to accommodate a variety of differentinterspinous spaces between vertebrae. Likewise, the lateral walls 36 ofdifferent spacer bodies 12 may be provided at different locations alongthe length of the superior sections 34, in order to provide a greatervariety of sizes and shapes. The surgeon can thus select a suitablyshaped and sized spacer body 12 depending on the particular vertebra tobe supported and the natural anatomy of the patient.

Further, the lateral walls 36 may also be adjustable with respect to thespacer body 12. For example, in one embodiment, the lateral walls 36 mayform an obtuse angle with respect to the superior section 34 beforeimplantation. The lateral walls 36 may be formed of a malleable materialsuch that, after implantation, the surgeon may compress the lateralwalls 36 together to reduce the gap between the lateral walls 36,thereby securely fixing the spacer body 12 to the spinous process of thevertebra. The compression may be accomplished, for example, by pinchingor squeezing the lateral walls 36 towards one another using surgicalpliers or forceps.

To further enhance the ability of the device 10 to be secured to thesurrounding bone and soft tissue once implanted, the device 10 mayinclude a number of surface modifications. For example, sections of thespacer body 12, lateral walls 36, anchors 18, and/or fixation rod 16 mayinclude surface alterations that may facilitate tissue attachment,bonding or fixation. These alterations may include surface teeth, barbs,beads, surface roughening, or the addition of bioactive agents to one ormore sections of the device 10. For example, the device 10 may includeone or more barbs 40 for securing the device 10 to bone and/or softtissue. As shown in FIGS. 7A and 7B, barbs 40 may be located on thespacer body 12, such as on an outer surface of the midsection 30,inferior section 32 and/or superior section 34 (FIG. 7B). Alternatively,or in addition, the barbs 40 may be located on an inner surface of thelateral walls 36 (FIG. 7A). The barbs 40 may help the spacer body 12securely engage connective tissue or a bony surface of a vertebra, suchas the spinous process of the vertebra.

Further, the device 10 may also include roughened or porous surfaces.The roughened or porous surfaces may enhance attachment between implantsurfaces and bone tissue. In addition, some porous surfaces mayfacilitate tissue ingrowth to form a biological bond between sections ofthe device 10 and the surrounding bone and/or soft tissue. Roughened orporous surfaces may be included on any portion of the device 10,including the spacer body 12, anchors 18, lateral walls 36, and/orfixation rod 16.

The surface of the device 10 may also include biologically activeagents. These agents may include osteogenic factors to furtherfacilitate bonding between components of the device 10 and thesurrounding bone and/or soft tissue. Further, the device 10 may includetherapeutic agents such as antibiotics, steroids, anti-thromboticagents, anti-inflammatory drugs, and/or analgesic agents. In oneembodiment, the biologically active agent may be contained in a coatingon the device. Alternatively, or in addition, the device may be porousand the biologically active agent may be contained in the pores of thedevice. The biologically active agent may be, for example, bonemorphogenic protein (BMP) for inducing cartilage or bone growth.

To further enhance the fixation of the spinous process within thestirrup 38 defined by the lateral walls 36 of the spacer body 12, thelateral walls 36 may be curved or angled with respect to thelongitudinal axis L of the spacer body 12. For example, FIGS. 8A and 8Bshow lateral walls 36 that curve away from the longitudinal axis L ofthe spacer body 12 along the length of the lateral walls 36. The lateralwalls or brackets 36 can also be bent or curved inwards or outwardsalong their length with respect to the longitudinal axis L of the spacerbody 12 to accommodate the patient's natural anatomical curves of thelaminae. FIG. 9A illustrates a spacer body 12 having lateral walls 36that bend inward with respect to the longitudinal axis L of the spacerbody 12. Such curved brackets 36 allow even greater conformity aroundthe spinous process 2, and therefore better fixation of the device 10 tothe vertebra 4, as shown in FIG. 9B.

In another exemplary embodiment, at least one of the lateral walls orbrackets 36 may be removably attachable to the spacer body 12. Forexample, as shown in FIGS. 10A-10C, one of the pair of lateral walls orbrackets 36A can be formed as an attachable element to the spacer body12, while the other lateral wall or bracket 36B is permanently affixedor integral with the spacer body 12. The attachable bracket 36B caninclude a first free end 42 and an opposed, second attachment end 44that is shaped to complement a slot or groove 46 on the superior section34, thereby forming a secure connection with the spacer body 12.

As shown in FIGS. 10A-10C, the attachment end 44 can be formed as aflared end or dovetail for sliding engagement with a dovetail groove 46on the superior section 34 once the spacer body 12 has been implanted inposition. FIGS. 11A-11C show an attachable bracket 36A having anattachment end 44 shaped as a “T” for sliding engagement with a T-shapedgroove 46 on the superior section 34 of the spacer body 12. Further,instead of slidably attaching to a groove 46 on a top surface of thesuperior section 34 of the spacer body, the attachable bracket 36A canslide onto a groove 46 which is formed on a side surface of the superiorsection 34. For example, as shown in FIGS. 12A-12C, the attachment end44 of bracket 36A is configured as a dovetail to slidingly engage adovetail groove 46 on a side surface of superior section 34 of spacerbody 12. Although attachment end 44 has been described hereinabove ashaving a dovetail or T-shaped configuration, it is understood that theattachment end 44 can include other shapes known to one skilled in theart for forming a secure attachment to a complementarily shaped groove46 on the superior section 34.

In yet another exemplary embodiment, instead of having a freelydetachable bracket 36A the spacer body 12 can include a movable,pivotable bracket 36A which can be hinged to the superior section 34.For example, as shown in FIGS. 13A-13C, the second, attachment end 46 ofbracket 36A can include an aperture 48 for placement of a pin 50therethrough to pivotably secure the bracket 36A to a side surface ofsuperior section 34. In this embodiment, the pivotable bracket 36A canbe folded down (FIG. 13A) prior to implantation and then after thespacer body 12 has been placed in its correct position, the pivotablebracket 36A can be folded up to rest against and engage the spinousprocess 2 of the vertebra 4, as shown in FIGS. 13B and 13C.

In still a further exemplary embodiment, the movable, adjustable bracket36A can be hinged to the superior section 34 of the spacer body, asshown in FIG. 14A. In this embodiment, the movable bracket 36A can beattached to the spacer body 12 by a hinge joint 52 that allows thebracket 36A to fold up and down. This foldability allows the bracket 36Ato move between a position in which the movable bracket 36A issubstantially perpendicular to the respective adjacent bracket 36B (FIG.14A), and a position in which the movable bracket 36A is substantiallyparallel to the adjacent bracket 36B (FIGS. 14B and 14C) to engage thespinous process 2.

The lateral walls or brackets 36 of the present invention can alsoinclude an aperture 60 for receiving a bone screw, fastener or rivet tofix the brackets 36 to the spinous process 2. Such fastening memberswould ensure that the brackets 36 are laid flat against the spinousprocess 2 in order to avoid any play of the process with respect to thebrackets 36. For example, as shown in FIGS. 14B-14C, each of thebrackets 36A, 36B can be provided with an aperture 60 configured toreceive a rivet or fastener 100, shown in greater detail in FIG. 15. Therivet 100 can include a cap 102, an elongate body 104 extending from thecap 102, the elongate body 104 including a plurality of teeth 108 andterminating at a tapered distal end 106. The elongate body 104 isconfigured to extend between the apertures 60 of the brackets 36A, 36B.A washer 120 can be provided to maintain the rivet 100 within theapertures 60. As shown in FIG. 14C and in greater detail in FIG. 14D,the washer 120 includes an aperture 122 for receiving the tapered distalend 106 of the rivet 100. Slots 124 around the aperture 122 enable thewasher 120 to flex so that the tapered distal end 106 can be pushedthrough the aperture 122 and the washer 120 to close around the teeth108 of the rivet 100.

FIGS. 16A-16D illustrate another exemplary embodiment of a bone fasteneror pin 140 suitable for use with the brackets 36 of the presentinvention. Fastener 140 includes a head 142, an elongate body 144 havingteeth 148 extending thereabout to a distal end 146. To secure thefastener 140 between the apertures 60, a cap 160 is provided which has ahead 162 and a body 164 extending therefrom for receiving the distal end146 of the fastener 140. As shown in greater detail in FIG. 16D, thehollow body 164 can include one or more U-shaped slots 166, with eachslot 166 defining a finger projection 168 therein. Each of the fingerprojections 168 has a curved end portion 170 bent towards the centralaxis of the hollow body 164 for engaging the teeth 148 of the fastener140, as illustrated in FIG. 16A and in greater detail in FIG. 16B. Inone exemplary embodiment, the cap 160 includes two pairs of fingerprojections 168, with each pair being diametrically opposed. The pairsof finger projections 168 can be staggered with respect to thelongitudinal axis A-A of the cap 160, thereby providing a morecontrolled level of attachment by providing two distinct areas withinthe slotted cavity 166 for capturing the teeth 148 of the fastener 140.In use, the cap 160 is placed through the aperture 60 of the bracket 36and then pushed towards the fastener 140 in a ratchet-like fashion untilthe heads 142, 162 of the fastener 140 and cap 160 are flush with theouter surface of the brackets 36, locking together the fastener 140 andcap 160 and thereby also providing an overall smooth outer surface thatprevents trauma or injury to the nearby soft or bony tissue.

It is also contemplated that the brackets 36 of the spacer body 12 maybe used with one or more flexible fixation elements to further securethe device 10 to one or more spinous processes. In one embodiment shownin FIG. 17A, the lateral walls or brackets 36 of flexible spacer body 12may include one or more apertures 60 for attaching a flexible fixationelement 180. The flexible fixation element 180 may include synthetic ornatural materials. For example, the flexible fixation element 180 mayinclude any type of synthetic or natural suture material. The flexiblefixation element 180 may also include grafts of ligaments, tendon,fascia, or muscle, and the grafts may include autografts, allografts, orxenografts having sufficient strength and pliability to tie around aspinous process of a vertebra, such as for example, a lumbar vertebra.Alternatively, the flexible fixation element may be a woven fabric,mesh, or webbing such as a cable-binder type strap for placement aroundthe spinous process.

FIG. 17B illustrates the spacer body 12 implanted between a sacrum 8 andspinous process 2 of an adjacent vertebra 4, while the fixation rod 16is secured to the sacrum 8 using two anchors 18. The lateral walls 36further secure the spacer body 12 to the spinous process 2 of thevertebra. In addition, the device 10 includes a flexible fixationelement 180, which may further secure the device 10 to the spinousprocess 2.

In still a further exemplary embodiment, as shown in FIGS. 18A-18C and19A-19C, a rigid fixation element may be used to secure the spacer bodyto the spinous process. As shown in FIGS. 18A and 18B, a stabilizationdevice 200 is provided which may include a rigid fixation elementcomprising a rigid fixation cap 220 for placement over a portion of thespacer body 202. The spacer body 202 may be similar to spacer body 12but without the lateral walls 36. The fixation cap 220 may be U-shaped,and include a pair of sidewalls 222, the terminal ends 224 of whichinclude a lip 226 defining a groove 228 for sliding engagement with aflange 206 on the superior section 204 of the spacer body 202 tosecurely attach the spacer body 202 to a spinous process 2, as shown inFIG. 18C. The fixation cap 220 can include barbs 210 for secureengagement with the bony surface of the spinous process, therebyensuring a rigid fixation.

FIGS. 19A-19C illustrate yet another exemplary embodiment wherein astabilization device 240 is provided with a rigid fixation elementcomprising a fixation cap 260 for placement over a portion of the spacerbody 242. The fixation cap 260 may be U-shaped, and include a pair ofsidewalls 262, the terminal ends 264 of which include a beveled flange266. Like spacer body 202, the spacer body 242 does not include lateralwalls 36. Instead, the spacer body 242 can include slots 246 on thesuperior section 244. Due to the slight flexibility and compressibilityof the sidewalls 262, the beveled flanges 266 can be forced down andthrough the slots 246, as shown in FIGS. 19A and 19B to engage thespacer body 242. The fixation cap 260 can include barbs 210 for secureengagement with the bony surface of the spinous process, therebyensuring a rigid fixation.

FIGS. 20A-20C illustrate an exemplary embodiment in which the spacerbody 12 of the present invention can be used with a rigid fixationelement. As shown in FIGS. 20A and 20B, a rigid fixation cap 280 isprovided for use with the spacer body 12 of the present invention. Therigid fixation cap 280 includes a pair of sidewalls 282 connected by aconnector section 284. Sidewalls 282 include teeth 288 on an insidesurface that can engage a notch 64 on an outer surface on the lateralwalls or brackets 36 of spacer body 12. In use, the fixation cap 280 canbe placed over the brackets 36 after the spacer body 12 is in positionand the vertebra's spinous process 2 resides securely within the stirrup38 defined by the brackets 36. By pushing downward on the fixation cap280, the teeth 288 within the sidewalls 282 can ratchet over and lockwith the notches 64 of the brackets 36 until the connector section 284of the cap 280 rests against the spinous process 2, and thereby ensuresa secure fit between the bony tissue and the device 10, as illustratedin FIG. 20C. The adjustability of the fixation cap 280 allows the spacerbody 12 to secure a variety of sized spinal processes. As shown, thelateral walls or brackets 36 can be provided with elongated slots 60similar to the elongated slots 290 on the sidewalls 282 of the fixationcap 280. When the fixation cap 280 is ratcheted onto the spacer body 12,the slots 60, 290 align and cooperate to provide an opening forplacement of an optional fixation element therethrough for furthersecurement of the spinous process to the spacer body 12, if desired. Thefixation element can be, for example, a bolt or bone screw that extendsthrough the spinous process or extends atop the process and across thetwo sidewalls 282.

The fixation caps 220, 260, 280 may be formed from a variety ofdifferent biocompatible metals materials, such as, for example, titaniumand stainless steel, or cobalt chrome, or biocompatible plastics, eitheralone or along with at least one other suitable material from thisgroup. The shape, dimensions, and materials of the fixation caps 220,260, 280 may be selected to control their physical properties such asflexibility, strength, and/or fracture resistance.

Turning now to the particulars of the anchor assembly 14 and the methodsfor securing the spacer body 12 to the sacrum, as shown in FIG. 21 thespacer body 12 may connect with the fixation rod 16 at a base portion 62extending from the inferior section 32. The base portion 62 may form apermanent connection or a removable connection. As illustrated in FIG.21, the spacer body 12 may include an aperture 64 within the baseportion 62 for engaging the fixation rod 16. In one embodiment, theaperture 64 may be a through hole for placement of the fixation rod 16therethrough. A plastic liner can be provided within the aperture 64 ofthe base portion 62 to facilitate a smooth, sliding movement of the rod16 within the aperture 64. The plastic liner can be formed from, forexample, a polyethylene, such as ultra high molecular weightpolyethylene (UHMWPE), or polyetheretherketone (PEEK).

In another embodiment, as shown in FIGS. 22A and 22B, the base portion62 may comprise a semi-circular or C-shaped section 66 for engaging thefixation rod 16. The C-shaped section 66 can be configured to be snapfitted onto the rod 16. It is contemplated that a plastic liner formedfrom, for example, a polyethylene, such as ultra high molecular weightpolyethylene (UHMWPE) or polyetheretherketone (PEEK) can be provided onthe rod 16 between the C-shaped section 66 in order to provide smoothgliding motion of the spacer body 12 against the rod 16.

Further, the spacer body 12 may be configured to be angularly rotatablewith respect to the longitudinal axis of the fixation rod 16. In oneembodiment, the spacer body 12 may be freely rotatable with respect tothe longitudinal axis of the fixation rod 16. In another embodiment, thefixation rod 16 may include one or more protrusions 68 for limiting therotation of the spacer body 12, as illustrated in FIG. 23. For example,the spacer body 12 may rotate between about 0 and about 60 degrees withthe protrusion 68 delimiting the space between which the spacer body 12can rotate. Such rotation may facilitate positioning of the spacer body12 during implantation, while also allowing a controlled degree ofpatient motion after implantation. It is contemplated that the surgeonmay select the degree of rotation available by selecting a fixation rod16 with a protrusion 68 having a predetermined size and shape.Alternatively, the spacer body 12 may be rigidly fixed to the fixationrod 16 so as not to allow any rotation.

In order to allow further flexibility in the orientation of the device10, either during the implantation process or after implantation, thespacer body 12 may also be configured to be laterally movable orslidable with respect to the fixation rod 16. As shown in FIG. 24, thefixation rod 16 may include one or more lateral protrusions 70 todelimit the space within which the spacer body 12 can slide. Thus, thelateral protrusions 70 may limit lateral displacement of the spacer body12 when attached to the fixation rod 16. In one embodiment, the lateralprotrusions 70 may be adjustably positioned on the fixation rod 16,thereby allowing the surgeon to select a desired degree of lateraldisplacement. Further, in one embodiment, the lateral protrusions 70 maybe positioned adjacent the spacer body 12 to prevent any lateralmovement of the spacer body 12 with respect to the fixation rod 16.Alternatively, fixation rod 16 may be configured to limit lateralmovement of the spacer body 12 (as shown in FIGS. 26A and 26B).

Turning now in particular to the fixation rod 16, the fixation rod 16may be configured to have a number of different shapes, sizes, and/ormaterial properties. In the embodiment of FIG. 1, the fixation rod 16 isa straight rod with a circular cross-section. FIGS. 25A-25C illustrateadditional cross-sectional geometries suitable for the fixation rod 16of the present disclosure. For example, the fixation rod 16 may have anoval cross-section (FIG. 25A), a square cross-section (FIG. 25B), or arectangular cross-section (FIG. 25C).

In addition, the fixation rod 16 may have a cross-sectional geometrythat is variable across its length. For example, as shown in FIG. 26A,the fixation rod 16 may include a connecting region 74 for engaging thebase portion 62 of the spacer body 12. The connecting region 74 may bethicker or thinner (as shown in FIGS. 26A and 26B) than the surroundingthicker sections 76 of the fixation rod 16.

In one embodiment, the fixation rod 16 may be configured to limitlateral movement of the spacer body 12. For example, as shown in FIG.26B, the fixation rod 16 may include a narrow connecting region 74.During production, the spacer body 12 may be connected to the fixationrod 16 at the narrow connecting region 74 by engaging the base portion62 thru the aperture 64. The surrounding thicker sections 76 may therebyblock lateral movement of the spacer body 12 on the fixation rod 16,while still allowing rotation of the spacer body 12 with respect to thefixation rod 16. Alternatively or in addition, the spacer body 12 may befused to the fixation rod 16 to prevent lateral movement and/or rotationwith respect to the fixation rod 16.

Like the spacer body 12, the fixation rod 16 may be formed from avariety of different biocompatible materials. For example, the fixationrod 16 may, e.g., be formed from titanium, stainless steel, ceramics, orcobalt chrome, either alone or along with at least one other suitablematerial from this group. The fixation rod 16 may comprise the samematerials as the spacer body 12 or different materials than the spacerbody 12. The shape, dimensions, and materials of the fixation rod 16 maybe selected to control the flexibility, strength, and/or fractureresistance of the fixation rod 16. The length and thickness may also beselected based on a patient's size, disease characteristics, and/oractivity level.

As shown in FIGS. 27A-27C, the fixation rod 16 may be straight, bent, orcurved along its length to accommodate the natural curves of thepatient's anatomy. For example, in one embodiment, the fixation rod 16may include at least one curved section 80 (FIG. 27A). In anotherembodiment, the fixation rod 16 may include at least two bent sections78 (FIG. 27B). The bent sections 78 may be formed at an angle a withrespect to a longitudinal axis of the fixation rod 16. The angle a maybe between 0 and 90 degrees. For example, the angle a may be about 30degrees (FIG. 27B) or about 90 degrees (FIG. 27C).

In use, the fixation rod 16 having a curved 80 or bent section 78 may beimplanted in a number of different anatomic orientations. For example,the bent section 78 may be positioned in a superior-anterior orientationwith respect to the longitudinal axis of the fixation rod 16. The exactorientation may be selected based on surgical factors and/or patientanatomy.

In some situations, it may be desirable to provide a spacer body 12′which can slide not only laterally but in the anterior-posteriordirection as well. FIGS. 28A and 28B provide such an exemplaryembodiment, in which the spacer body 12′ includes an elongate or ovalbase portion 84 with a corresponding elongate or oval aperture 86 foruse with a cylindrical rod 16 of the present invention. In all otheraspects, spacer body 12′ is similar to spacer body 12 previouslydescribed, whereby similar features are designated by the same referencenumerals. To facilitate a smooth gliding motion between the base portion84 and rod 16, a plastic liner 88 can be provided within the aperture86. The plastic liner can be formed from any suitable plastic, such as,for example, ultra high molecular weight polyethylene (UHMWPE) orpolyetheretherketone (PEEK). When implanted within a patient, theelongate base portion 84 provides sufficient clearance for the spacerbody 12 to glide back and forth in an anterior to posterior directionduring flexion and extension of the vertebral column.

FIGS. 29A-29C illustrate yet another exemplary embodiment of a spacerbody 12″ which can translate about the anterior-lateral direction withrespect to the fixation rod 16″. As shown in FIG. 29A, the spacer body12″ includes an inferior section 32 having a raised socket 90 defining aspherical groove or cavity thereunder 92. The spherical cavity 92 isconfigured to sit against a spherical protrusion or knob 94 on fixationrod 16″. In all other aspects, the spacer body 12″ and the fixation rod16″ are similar to the spacer body 12 and fixation rod 16 previouslydescribed, whereby similar features are designated by the same referencenumerals. In use, the raised socket 90 is positioned over and sits onthe spherical protrusion or knob 94, creating a ball-and-socket typejoint. Such a connection would allow the spacer body 12″ to rotatefreely with respect to the rod 16″ and thereby provide the patient witheven greater flexibility and degree of motion, especially duringtwisting or bending movements, but still providing a rigid, fixedattachment to the vertebra being supported.

To secure the fixation rod 16 to the patient's sacrum or other bonesurface, fixation elements may be provided. The fixation elements mayinclude anchors 18 that attach to the fixation rod 16 at one or moreanchor-connecting regions 110. Anchor-connecting regions 110 may includeprotrusions, as illustrated in FIG. 30. Additionally, theanchor-connecting regions 110 may comprise indentations, concavities,convexities, or anchor through-holes, as shown in FIG. 22B. The designof anchor-connecting regions 110 may be selected based on the design ofthe particular type of anchor 18 being used. It is contemplated that thedesign and type of anchor 18 can vary without departing from the spiritof the present disclosure. For example, the anchors 18 may include anytype of screw that may securely engage bone.

Turning now to the particulars of the fixation element or anchor 18shown in FIG. 1, the anchor 18 may comprise a polyaxial screw, which maybe aligned in a range of angular orientations with respect to thefixation rod 16. Thus, the polyaxial screws may allow the surgeon toeasily adjust the position of the screw during surgery and consequentlythe fixation rod 16 based on anatomic variances of the patient.

In one exemplary embodiment, the anchor 18 can be similar to the onedisclosed in U.S. Pat. No. 6,554,831 to Rivard, which is herebyincorporated in its entirety by reference. As shown in FIGS. 1 and 26B,the polyaxial screw 20 is captured within a C-shaped collar such asclamp collar 22 that fits around the fixation rod 16. The screw 20 caninclude a proximal threaded portion 24 that extends through the collar22 and is fixed in place by tightening nut 26, and a distal threadedportion 28 that enables the screw 20 to anchor to bone tissue.

It is understood, of course, that a number of differently designedpolyaxial screws may be used with the present invention in order toprovide the surgeon with the ability to secure the fixation rod 16 tothe patient in an effective manner. An exemplary embodiment of apolyaxial screw 300 suitable for use with the present invention is shownin FIGS. 30, 31A and 31B. As illustrated, the polyaxial screw 300includes an elongated threaded body 302 extending between a head portion304 and a distal end 306. The threaded body 302 can be straight orangled or curved, depending on the particular need of the patient. Thehead portion 304 includes a hollow spherical cavity 308 for receiving ananchor-connecting element, which in this embodiment takes the form of aspherical clamp ring 320. The spherical clamp ring 320 includes slots322 distributed around its periphery to enable the clamp ring 320 toflex and slidingly fit over a fixation rod 16.

The head 304 also includes a plurality of spherical undercuts 328,creating curved inclined walls, and slots 326 extending therein at thebottom of the cavity 308, which are disposed so that they aresubstantially radial in relation to the cavity 308. These slots 326 andundercuts 328 converge toward one another in the direction of the bottomof the cavity 308 and give a slight flexibility to the head 304. Inaddition, the undercuts 328 enable the slotted spherical clamp ring 320to snap on inside the hollow spherical cavity 308. Two threaded holes330 are also provided on the head portion 304 for receiving threadedscrews 318.

A locking cap 310 is provided which comprises screw holes 312 forreceiving the threaded screws 318. The screw holes 312 coincide with theholes 330 on the head portion 304. The locking cap 310 also includes ahollow cavity 314 suitably shaped to receive a portion of the sphericalclamp ring 320, as illustrated in FIG. 31A. For example, the hollowcavity 314 can have a cone shape, permitting the cap 310 to come intocontact with the spherical clamp ring 320 in the course of tighteningthe screws 318. The hollow cavity 314 can also include lateral undercutsand slots similar to those present in the spherical cavity 308 of thehead portion 304 to enable the screw 300 to adjust angularly prior tobeing locked together, as shown in FIG. 31B.

In use, the spherical clamp ring 320 is snap-fitted onto the hollowcavity 308 of the head portion 304 of the screw 300, the clamp ring 320being held by the engagement of the slots 322 of the clamp ring 320 andthe undercuts 328 of the head portion 304. The clamp ring 320 with thehead portion 304 and threaded body 302 is then slid over the fixationrod 16 and positioned at an anchor-connecting region of the rod 16. Thecap 310 is then positioned over the clamp ring 320 and the threadedscrews 318 inserted through the screw holes 312, 330 and tightened. Theentire process can be repeated, since a plurality of screws 300 can beused with any given fixation rod 16, depending on the needs of thepatient.

In FIG. 29B, a similar polyaxial screw 340 is shown, but with a modifiedhead portion 344. Like the polyaxial screw 300 previously described,polyaxial screw 340 includes an elongated threaded body 342 extendingbetween a head portion 344 and a distal end 346. The threaded body 342can be straight or angled or curved, depending on the particular need ofthe patient. The head portion 344 includes a hollow spherical cavity 348for receiving an anchor-connecting element, such as, for example, thespherical clamp ring 320 of FIG. 30. As with the previous embodiment,the head portion 344 can include a plurality of spherical undercuts 352,creating curved inclined walls, and slots 350 extending therein at thebottom of the cavity 348. A threaded hole 354 is also provided on thehead portion 344 for receiving a threaded screw 370. At an opposite endof the head portion 344 is a raised flange 356 which creates a groove358 for slidingly receiving a locking cap 360, as shown in FIGS. 29B and29C.

Locking cap 360 is provided with a lip 372 at one end and at an oppositeend a single screw hole 362 for receiving the threaded screw 370. Thescrew hole 362 coincides with the hole 354 on the head portion 344. Thelip 372 enables the cap 360 to slide over the head portion 344 andengage with the groove 358 prior to insertion of the threaded screw 370.The lip 372 of the locking cap 360 and corresponding groove 358 of thehead portion 344 can be configured to provide a slight gap or clearancesufficient for the locking cap 360 to be able to flip up to about a90.degree. angle with respect to the head portion 344 without becomingdislodged, thereby creating a hinge between the cap 360 and the headportion 344. Alternatively, the locking cap can be configured to attachto the head portion via a hinge joint. Further, as with the previouslydescribed embodiment, the locking cap 360 can also include a hollowcavity 364 suitably shaped to receive a portion of the anchor-connectingelement 110, which hollow cavity 364 can also include lateral undercutsand slots similar to those present in locking cap 310.

Yet another exemplary embodiment of a polyaxial screw 380 suitable foruse with the devices 10 of the present invention is shown in FIGS. 22Band 28B. In these embodiments, fixation rod 16 can be attached at bothends to a plate 390 having a spherical countersink 392 with athrough-hole for insertion of the polyaxial screw 380 therethrough. Theplate 390 can be clamped onto the rod 16, or it can be configured withan aperture for sliding engagement of the rod 16 into the plate 390itself. The polyaxial screw 380 includes an elongate threaded body 382extending from a spherical head 384 into a distal end 388. The sphericalhead 384 includes a hexagonal opening 386 for receiving an insertiontool (not shown). In use, the spherical head 384 of the polyaxial screw380 can be angularly adjustable within the spherical countersink 392 ofthe plate 390 prior to being secured to bone tissue.

While rod-based systems have been described for anchoring the spacerbody 12 to the sacrum or other bone tissue, FIGS. 32A-41 provideadditional exemplary embodiments of spacer bodies that do not require arod to be attached to the sacrum. In FIG. 32A, a spacer body 400 isshown having similar features to the spacer body 12 of previouslydescribed embodiments, wherein the same features are designated by thesame reference numeral. Spacer body 400 includes a pair of angled legs402 extending from the inferior section 32 of the spacer body 400. Thelegs 402 lie in a plane that is substantially parallel to the planescontaining the brackets 36, and can include surface features such as,for example, barbs 404 for engagement with bone tissue. The legs 402collectively form an anchor assembly 406 portion comprising a grippingportion 416 for attachment to the sacrum. A backplate 410 can optionallybe provided which extends from the inferior section 32 and lies in aplane that intersects with the planes containing the brackets 36. Inuse, the legs 402 are configured to rest against the median crest of thesacrum 8, while the backplate 410 rests within the sacral canal andagainst the sacrum 8, as shown in FIG. 32B. Thus, the legs 402 andbackplate 410 provides a passive bone-engaging region which allows thespacer body 400 to be inserted and secured onto the sacrum without theneed for injury or trauma to the bone resulting from screw fixation.

In FIG. 33A, a spacer body 400′ is shown having an anchor assembly 406comprising two backplates 410 extending from the inferior section 32 atan angle away from one another. Each of the backplates 410 can also beslightly curved along its longitudinal axis. As shown in FIG. 33B, whenin use the spacer body 400′ rests against the sacrum such that the twobackplates 410 rest against the sacrum inside the sacral canal, and legs402 hook onto the median crest of the sacrum 8. The two backplates 410are configured to provide sufficient clearance between them so as toavoid impinging any nerve tissue contained within the sacral canal oncethey are inserted into the canal.

Instead of having a backplate 410, the spacer body 420 of FIG. 34Aincludes an anchor assembly 406 comprising a spike 422 extending fromthe inferior portion 32 at an angle generally parallel to the legs 402.The spike 422 can have a sharp pointed tip, as shown. In use, the spike422 is configured to pierce into the sacral bone tissue while the legs402 engage the median crest, thereby allowing the spacer body 420 to bein position and rest on the sacrum, as illustrated in FIG. 34B. Althoughthe legs 402 of the present embodiments are shown as plates extendingfrom the spacer body, it is contemplated that the legs 402 can comprisehooks, barbs, jaws, or any suitable gripping element.

FIGS. 35A and 35B show yet another exemplary embodiment of a spacer body440 which includes an anchor assembly 406 comprising a pair of endplates432 extending from the inferior section 32 of the spacer body 440, eachendplate 432 having a screw hole 434 for insertion of a screw 436therethrough. In use, the endplates 432 can be positioned between thesacral canal and the outer surface of the sacrum, and a screw 436 placedthrough the bone tissue and secured through the endplates 432 with a nut438. It is contemplated that more than one screw 436 may be implementedin the present embodiment. For example, the endplates 432 may beconfigured to allow for two or more screws 436 to be placed in anysuitable orientation relative to one another, such as in a horizontal orlongitudinal row. Alternatively, two or more screws 436 may be insertedthrough the endplates 432 such that screws 436 flank the median sacralcrest. In one embodiment, the spacer body 440 can be provided with twopairs of endplates 432, with each pair of endplates being configured togrip onto a portion of the sacrum, the two pairs of endplates flankingthe median sacral crest. The endplates 432 may, of course, be providedwith any suitable number of screw holes for insertion of bone screws 436therethrough. Such embodiments would provide rigid and secure fixationof the spacer body 440 to the sacrum.

Rather than having two endplates 432, FIGS. 36A and 36B show anexemplary embodiment in which the spacer body 450 includes a singleendplate 452 extending at about a 90.degree. angle with respect to theinferior section 32 of the spacer body 450. As shown, the endplate 452can include barbs 404 and a plurality of screw holes 454 for placementof screws 456 therethrough. The endplate 452 can be configured with asubstantially U-shaped body and a pair or more of screw holes 454extending along the length of each leg of the U. The opening provided bythe U-shape allows the endplate 452 to accommodate the spinous process,thereby avoiding the need to resect any part of the bone tissue. Ofcourse, it is understood that the endplate 452 can take any shape and/orsize suitable for placement against a sacral surface, and that anynumber of screws 456 can be applied in order to achieve a rigid andsecure fixation to the bone tissue. In use, the endplate 452 isconfigured to rest against the outer surface of the sacrum 8 when thespacer body 450 is in position within the patient, as shown in FIG. 36B.

FIGS. 37A and 37B show still yet another exemplary embodiment in whichthe spacer body 450′ has a detachable endplate 452. The spacer body 450′has a shape similar to that shown in FIG. 22A, with the base portion 62having a C-shaped claw section 66 for snap fitting onto a rod-likeattachment end 460 of the detachable endplate 452. Such a configurationwould enable the endplate 452 to be rotatable with respect to the spacerbody 450′ and thereby provide flexibility for the surgeon duringimplantation. A plastic liner formed from, for example, a polyethylene,such as ultra high molecular weight polyethylene (UHMWPE), orpolyetheretherketone (PEEK) can be provided between the rod-likeattachment end 460 and the C-shaped section 66, in order to providesmooth gliding motion of the spacer body 12 against the plate 452.

FIGS. 38A and 38B show an exemplary embodiment in which the spacer body500 can include a midsection 30, inferior 32 and superior 34 sections,and lateral walls or brackets 36 similar to spacer bodies previouslydescribed and shown. As previously discussed, the midsection 30 may havevarying thickness or dimensions along its length to provide varyingphysical properties, or may be shaped or curved as shown, in order tobetter adapt to the anatomical features of the patient. The lateralwalls or brackets 36 may include an aperture 60 for receiving a fastenersuch as, for example, a rivet. Further, the spacer body 500 may alsoinclude surface alterations such as barbs or teeth 40, 512 to facilitatetissue attachment, bonding or fixation. At least one backplate 410 mayextend from the inferior section 32. The backplate 410 may be positionedwithin the sacral canal and against the sacrum when implanted.

A side cap or panel 502 may be provided for attachment to the spacerbody 500. The side cap or panel 502 may include a midsection 506, whichmay also be similarly shaped and configured as the midsection 30 ofspacer body 500, as well as an inferior section 508 and superior section504. The inferior section 508 may include a groove (not shown) forreceiving a tongue 510 extending from the inferior section 32 of thespacer body 500. The inferior section 508 may further include grooves516 for latching to a notch 514 provided on the tongue 510. Legs 402 mayextend from the inferior section 508 for hooking onto the median crestof the sacrum 8. The superior section 504 may include a wedge 518 thatrests against the outer surface of the superior section of the spacerbody 500. A ramp 520 may be provided on the spacer body 500 to limit theextension of the wedge 518 through the brackets 36.

In use, the spacer body 500 may be first inserted by placing thebackplate 410 around the sacrum, and positioning the spinous process 2of the L5 vertebra in between the lateral walls or brackets 36. Next,the side cap or panel 502 may be placed against the spacer body 500 suchthat the wedge 518 extends under the spinous process and the tongue 510of the spacer body ratchets into the groove of the cap 502. The legs 402of the cap may be hooked onto the median crest of the sacrum 8, as shownin FIG. 39.

FIGS. 40A and 40B show another exemplary embodiment in which the spacerbody 550 can comprise a two-component assembly. The first component ortop portion 552 may include a midsection 30, a superior 34 section, andlateral walls or brackets 36 similar to spacer bodies previouslydescribed and shown. As previously discussed, the midsection 30 may havevarying thickness or dimensions along its length to provide varyingphysical properties, or may be shaped or curved as shown, in order tobetter adapt to the anatomical features of the patient. The lateralwalls or brackets 36 may include an aperture 60 for receiving a fastenersuch as, for example, a rivet. Further, the spacer body 550 may alsoinclude surface alterations such as barbs or teeth 40, 512 to facilitatetissue attachment, bonding or fixation. The midsection 30 may extendinto an inferior platform 580 having a dovetail projection 582 and agroove 584 thereon, as shown in FIG. 40A. The second component or bottomportion 554 may include a superior platform 570 having a groove 572thereon and a notch 574 inside the groove 572 to form a dovetailconnection with the inferior platform 580 when the first and secondcomponents are assembled, as shown in FIG. 40B. A backplate 410 and legs402 similar to those previously shown and described may be provided onthe second component 554.

In use, the second component 554 may be placed onto the sacrum 8, withthe backplate 410 resting within the sacral canal and the legs extendingaround the median crest of the sacrum 8, as shown in FIG. 41. Next, thefirst component 552 may be secured onto the second component 554 bysliding the dovetail projection 582 into the groove 572 of the secondcomponent 554, and allowing the groove 584 to catch the notch 574. Thespinous process 2 of the L5 vertebra may be positioned within thelateral walls or brackets 36.

It is contemplated that the surgeon may use the devices of the presentdisclosure to treat a number of clinical problems. For example, thedevices may be used to treat degenerative disc disease and/or discherniation. The devices may also be used to treat spinal stenosis,including central and/or lateral canal stenosis. The devices may be usedbefore, after, or in conjunction with other treatments or implants,including adjacent rigid fixation, adjacent spinal decompression,fusion, and/or facet replacement or repair.

The devices of the present disclosure may be surgically implanted in avariety of ways without impairing the effectiveness of the devices. Forexample, the surgeon may select a number of different operativeapproaches and/or incision positions and/or sizes. Further, the surgeonmay implant each of the components of the devices in various sequences.The specific operative procedures may be selected based onpatient-specific clinical factors.

A number of different incisions and/or operative procedures may be usedto implant the devices of the present disclosure. For example, in oneembodiment, the surgeon may use a mid-line incision over the lumbar andsacral vertebrae to expose the L5-S1 interspinous region. Alternatively,the surgeon may use one or more incisions positioned lateral to thespine. Further, the surgeon may use a minimally-invasive procedureincluding various scopes, cannula, and/or robotic implantation devicesto deliver the devices to the surgical site.

After making appropriate incisions to expose the operative region, thecomponents of the devices may be implanted using several different stepswhich may be performed in a number of different sequences. For example,the surgeon may first implant one or more anchors 18 to the sacrum andthen implant spacer body 12 in the L5-S1 interspinous space. The spacerbody 12 may then be fixed to the fixation rod 16, which may finally besecured to the sacrum 8.

In another technique, the surgeon may first implant the spacer body 12.Anchors 18 may then be secured to the sacrum and the fixation rod 16 maybe secured to the anchors 18. The surgeon may complete the procedure bysecuring the device 10 to the spinous process of the vertebra using oneor more ligaments, sutures, and/or rigid fixation caps 220, 260, 280.

Further, the devices may be provided in a partially assembled form. Inthis embodiment, the spacer body 12 may be pre-assembled and securelyfixed to the fixation rod 16. Thus, the spacer body 12 may have apredetermined degree of lateral movement or rotation with respect to theattached fixation rod 16.

In another aspect of the disclosure, the devices may be assembled from amodular kit. The surgeon may individually select the size, shape, and/orphysical properties of each component, including the spacer body 12,fixation rod 16, anchors 18, flexible fixation element 180, and/orfixation caps 220, 260, 280. The surgeon may then assemble thecomponents and select an appropriate degree of lateral movement and orrotation for the spacer body 12 and fixation rod 16 as needed.

The anchors 18 may be secured to sacral bone in a variety oforientations. For example, in one embodiment, the device 10 may includetwo polyaxial screws. The polyaxial screws may be inserted on oppositesides of the sacrum 8. The polyaxial screws may be inserted into thesacral alae or pedicle and may be directed in an anterior-lateraldirection. The surgeon may choose a different orientation and anchorplacement based on clinical factors such as surrounding bone diseaseand/or prior surgery or implants.

It is contemplated that the devices 10 of the present disclosure mayprovide an improved system and method for treating various disorders ofthe spine. For instance, the devices provide a mechanism for treatingdisorders of the spine at the L5-S1 vertebral level. Further, thedevices of the present disclosure may also be useful for treatingdiseases of the spine at other vertebral levels. However, the devices ofthe present invention may also be used to stabilize lumbar vertebraeabove the L5 level. For example, in the case of an L5 laminectomy, it ispossible to use the present device to stabilize the L4 vertebra whileplacing the screws of the rod-based device system into the pedicles ofthe adjacent L5 vertebra, thereby providing a supporting bridge betweenthe L4-L5 region. Accordingly, it is contemplated that the devicesprovided in this disclosure, and in particular the rod-based systems,may be used to stabilize any pair of adjacent vertebrae by securing theanchors of the rod to the pedicles of the adjacent vertebra to thespinous process being supported.

Furthermore, it is contemplated that the devices of the presentinvention can be used as an interspinous vertebral stabilization implantfor placement between two or more adjacent vertebrae. This can beaccomplished by providing devices which have substantially similarfeatures both inferior and superior to the midsection 30 of the spacerbody 12. For example, it is possible to provide devices which havebrackets 36 similar to those described in FIGS. 10A-14D extending fromthe superior section 34 as well as the inferior section 32. Similarly,it is contemplated that an implant can be provided which has flanges206, slots 246, or notches 64 on the inferior section 32 as well as thesuperior section 34, as illustrated in FIGS. 18A, 19A, and 20A, for usewith a fixation cap 220, 260, 280 on both ends of the device.

The methods and devices of the present disclosure may be significantlyless invasive and/or produce less drastic and more reversible anatomicchanges as compared to other procedures including spinal fusion andtotal disc replacement. The device of the present disclosure may limitnormal spinal motion but provide some controlled movement in flexion,extension, rotation, and/or lateral bending. Further, the devices andmethods of the present disclosure may be particularly well-suited fortreating various stages of degenerative disc and/or spinal stenosis,particularly at the L5-S1 level.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

What is claimed is:
 1. A lumbosacral interspinous stabilization device,comprising: an inferior section, a superior section extendingsubstantially parallel to the inferior section, and a flexible U-shapedmidsection connecting the inferior section to the superior section, theinferior section, superior section and midsection together forming asubstantially U-shaped spacer body configured to extend into theinterspinous space, and further including a pair of lateral wallsextending from the superior section for engaging a spinous process of alumbar vertebra, and a plurality of projections extending from theinferior section, the plurality of projections including a pair ofendplates configured to grip therebetween a portion of a sacrum, eachendplate including at least one screw hole for receiving a bone screw,the bone screw being configured to extend through the at least one screwhole of one endplate, through bone tissue, and out the at least onescrew hole of the other endplate.
 2. The device of claim 1, wherein thelumbar vertebra is a fifth lumbar vertebra (L5).
 3. The device of claim1, wherein the flexibility of the body varies along its length.
 4. Thedevice of claim 1, wherein the thickness of the body varies along itslength.
 5. The device of claim 1, wherein the width of the body variesalong its length.
 6. The device of claim 1, wherein the lateral wallsextend substantially parallel to one another prior to implantation. 7.The device of claim 1, wherein the lateral walls extend away from oneanother prior to implantation.
 8. The device of claim 1, wherein thelateral walls are configured to be movable towards one another afterimplantation.
 9. The device of claim 1, wherein the lateral walls aremalleable.
 10. The device of claim 1, wherein each lateral wall containsa through hole.
 11. The device of claim 10, further comprising aflexible fixation element configured to be tied around the through holesand around the spinous process.
 12. The device of claim 11, wherein theflexible fixation element is a synthetic or natural material.
 13. Thedevice of claim 12, wherein the synthetic or natural material isselected from the group consisting of ligament, tendon, fascia, muscle,suture material, fabric, mesh, and webbing.
 14. The device of claim 10,further including a fastener for placement between the through holes ofthe lateral walls.
 15. The device of claim 14, further including a capfor placement over a distal portion of the fastener.
 16. The device ofclaim 14, further including a washer for placement over a distal portionof the fastener.
 17. The device of claim 1, wherein the device includessurface features for enhanced fixation to bone tissue.
 18. The device ofclaim 17, wherein the surface features are selected from the groupconsisting of teeth, barbs, beads, and surface roughening.
 19. Thedevice of claim 1, wherein the device further includes a biologicallyactive material to promote tissue growth after implantation.
 20. Thedevice of claim 19, wherein the biologically active material iscontained in a coating on the device.
 21. The device of claim 19,wherein the device is porous and the biologically active material iscontained in the pores of the device.
 22. The device of claim 1, whereinthe device is comprised of a biocompatible metal or polymer.
 23. Thedevice of claim 22, wherein the biocompatible metal or polymer isselected from the group consisting of titanium, titanium alloy,stainless steel, cobalt chrome, ceramics, ultra high molecular weightpolyethylene and polyetheretherketone.